Whale strandings

An unusual species of mammals, whales are classified in the order Cetacea, the same order that includes dolphins and porpoises. Whales are warm blooded, breathe air and have lungs, bear live young and nurse them on milk. But unlike other mammals, they live completely in the water. That's why ancient civilizations believed whales were fish until the Greek philosopher Aristotle noted that both whales and dolphins breathed through blowholes and delivered live babies instead of laying eggs.

There are two suborders of whales that have evolved differently over time. Baleen whales (suborder Mysticeti) are named after the Norse word for "grooved," because the 10 species have large grooves or pleats on their throats and bellies. Whales in this suborder lack teeth and feed mostly on small fish and plankton . Yet even with this relatively small-sized diet, they can grow extremely large. The blue whale, the largest species on record, can reach lengths of more than 100 ft (30 m) and weigh over 150 tons. Other baleen species include the grey whales, minke whales and humpbacks.

Toothed whales (suborder Odontocoti) are typically smaller and faster moving species, including the orca, narwhal, beluga, and the smaller dolphins and porpoises. These whales use their speed and agility to capture prey; the orca often feeds on marine mammals and birds. The majority of toothed whales feed mainly on fish and squid.

In order to find prey in dark or murky waters, toothed whales depend on a sense called echolocation. In fact, whales generally have good vision but it is limited to 45 ft (13.7 m). Their sense of hearing is more remarkable and water is an excellent conductor of sound. Echolocation works by bouncing signals off of objects ahead. Whales can then locate prey and navigate through water, judging water depth and shoreline. Toothed whales have more refined echolocation systems, while the echonavigation abilities of baleen whales are believed to be more rudimentary.

Whale strandings occur when whales swim or float to shore and cannot remove themselves. The mammals are then stuck in the shallow water. Usually, the cause of strandings is not known, but some causes have been identified. Whales may come to shallow water or to shore due to starvation, disease, injuries or other traumas, or exposure to pollution . Most stranded animals are found dead or die quickly after they are found. However, there have been cases in which stranded whales have been successfully moved to a rehabilitation facility, treated, and then released to the wild. Sea World facilities in Texas and Florida provide rescue and rehabilitation for stranded whales as do other organizations such as Greenpeace and the Atlantic Large Whale Disentanglement Network.

In recent years, underground explosions and military sonar tests may have caused otherwise unexplainable whale strandings off the coasts of Greece and the Bahamas. Over the course of two days in 1996, 12 whales beached on the coast of Greece and eventually died. These sorts of mass strandings are quite rare, and although the exact cause was not identified, it was discovered that the North Atlantic Treaty Organization (NATO) was testing an experimental sonar system in the area around the same time. No scientific connection could be proved, but no other physical explanation for the whales' beachings could be found.

In March 2000, 16 whales became stranded on two beaches in the Bahamas. Necropsies (animal autopsies) were performed on six of the seven that died and no signs of disease, poisoning or malnutrition were evident. However, the United States Navy had been performing underwater sonar experiments nearby that emit loud blasts underwater. An auditory specialist involved in the necropsies reported finding hemorrhages in or around the whales' ears. If the whales lost their echolocation capabilities, they would not be able to note the approaching shoreline, possibly explaining the mass stranding.

Environmentalists and scientists struggle to explain and lessen occurrence of whale strandings. Whales' social behavior is such that many species travel in strongly bonded groups. The urge to avoid separation from one another may be stronger than that of avoiding the fatal risk of stranding alongside one whale that is sick or injured and seeking shallow water.

A variety of other causes may bring about whale strandings. Pollution causes illnesses in whales that are unusual to their species and damage their nervous and immune systems. A group of killer whales stranded off the coast of British Columbia in the 1990s revealed the highest levels of mercury ever recorded for cetaceans.

Even weather patterns and water temperature can lead to whale strandings. Unfortunately, many strandings go undiscovered and the whales cannot be saved. What's more, the beached whales are usually not discovered in time for a useful necropsy so the strandings' cause is not determined. African stranding coordinators have been selecting samples from stranded whales for 50 years and have yet to identify any particular pattern that explains the reason for the phenomenon. One theory is that the continent's sandy sloping beach is more difficult to detect by the whales' sonar system than a more-defined, rocky coastline. Efforts to protect whales from hunting , polluting of their waters and strandings are increasing around the world.

[Teresa G. Norris ]

RESOURCES

BOOKS

Greenaway, T. Whales. Austin, TX: Raintree, Steck-Vaughn, 2001.

PERIODICALS

Milius, S. "Whales Stranded During Military Test." Science News 153 (March 21, 1998): 184.

Thurston, H. "Poisoned Seas: The Cause of Whale Strandings?" Canadian Geographic 115 (January-February 1995): 68.

ORGANIZATIONS

Save the Whales, PO Box 3650, Georgetown Sta., Washington, DC USA 20007 (202) 337-2332, Fax: (202) 338-9478, Email: [email protected], http://www.awionline.org/whales/indexout.html

Great Whales Foundation, PO Box 6847, Malibu, CA USA 90264 (310) 317-0755, Fax: (310) 317-1455, Toll Free: (800) 421-WAVE, Email: [email protected]